Cathode ray deflection coils



Nov. 20, 1956 w. REINHARD 2,771,563

CATHODE RAY DEFLECTION coms Filed Nov. 8, 1951 FIG.

INVENTOR W. BI'EIN` RD ATTORNEY United States Patent() CATHODE RAY DEFLECTION COILS Wolfgang Reinhard, Pforzheim, Germany, assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application November 8, 1951, Serial No. 255,353

Claims priority, application Germany November 10, 1950 Claims. (Cl. 313--76) This invention relates to improvements in electron tubes of the cathode ray type.

A primary object of the invention resides in the provision of improvements in cathode ray tubes of the magnetic deflection toroidal core type to distinguish from the electrostatic or magnetic deflection yoke type, and particularly to tubes of this type adapted for television receiver use.

An important object of the invention is to provide improved electro-magnetic deflection coils, using toroidal cores which will permit the pivotal point about which the electron beam is pivoted from the normal axis thereof outwardly through the conventional vflared portion of the tube, to be moved forward and closer to the tube screen.

Still another object resides in the provision of improved operation of cathode ray tubes of the magnetic deflection type permitting substantially decreased production costs over prior art tubes of comparable effective screen area.

Other objects and advantages are generally to improve and simplify cathode ray tube structure for one or more of the above stated objects, as will become readily apparent to persons skilled in the art upon examination of the drawings, specification and appended claims.

In the drawings, in which like parts are identified by the same reference numerals:

Fig. 1 is a longitudinal view, partially in section, of a cathode ray tube of the magnetic deflection type and incorporating the principles of the present invention.

Fig. 2 is a similar View, used for purposes of comparison, of a cathode ray tube of known type and employing prior magnetic deflection coils.

Fig. 3 is a view, showing partially in longitudinal section, an alternate embodiment of the invention.

Many cathode ray tubes currently employed in television receivers and for other uses, include a flared section, the walls of which extend laterally at a substantially large angle of, for example, 45 degreesor more for the purpose of providing the maximum effective screen area, or so-called picture size, This is true even in respect to tubes with relatively short neck portions, since public demand for a maximum picture size has resulted in a need for larger tubes of a type which can be produced at a relatively low manufacturing cost.

It is generally conceded that results obtained lin tubes of the type employing magnetic deflection coils are superior, at least for tubes in the same price range, to tubes employing electrostatic deflection. The former type tubes are almost universally employed in currently manufactured television receivers. Many advantages are inherent in magnetic deflection tubes, the principal advantage residing in a much wider deflection than is obtainable by the electrostatic method. `Certain factors have however imposed limitations on the picture size for a given type tube. It is common practice to dispose the deflecting coils, usually four in number on so-called television type tubes, as far forward of the tube neck as practical, and in some cases to have these coils overlie a part of the flared portion.

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A limiting factor as to forward disposition of the coils has been the position of abutment of the coils against the flared portion of the tube envelope. While in certain structures of this type, a minor portion of the deflecting coil may, in some instances, extend slightly beyond the base of the flared portion, a major portion of the coil has heretofore been disposed along the neck thereof with the result that the focal point about which the electron screen is deflected has been positioned substantially aft of the base of the flared portion. Since the position of the focal point limits the picture size to an area of slight ly less than that defined by an electron beam which is deflected sufficiently to strike the inner wall at the base of the flared portion, increasing the flare angle of the tube envelope beyond normal practice has heretofore not been desirable, since no attendant increase in picture size is obtained due to the above stated limi-tations, The present invention removes the limitations heretofore considered inherent in cathode ray tubes of this general type, and permits substantially increased picture size for tubes of the same neck diameter, and hence of substantially the same production cost.

Referring to Fig. 2, wherein a cathode ray tube of the toroidal core, magnetic deflection type of known design is shown for the purpose of illustrating the prior art, an envelope, generically designated 10, includes cylindrical neck portion 11 which leads at 12 into a flared portion 13 which -terminates in an end wall 14, the inner surface of which is conventionally provided with the socalled phosphor coating, or screen not shown. A magnetic coil, generically designated 16, one of four circumferentially disposed about the neck portion 11 conventionally includes toroidal iron core 17 about which is wound a suitable coil 18, the details of which are readily understood by persons skilled in the art. It may be assumed, wnile not shown, that the four such coils 18, one of which is illustrated in cross-section, encompass the neck portion 11, each coil extending circumferentially through an arc of less than a quadrant to provide the conventional pairs of vertical and horizontal deflecting coils with intervening spaces. The electron beam indicated at 20, initiated and focussed in a known manner not shown, at the base of the tube, unless deflected, travels outwardly to hit the end wall at 22. When deflected by energization of coil 18, the beam 20 may be deflected in the position shown along path 24 to strike the end wall 14 at 25. It is noted that such deflection starts a-t a point 27, located substantially midway between the ends of coil 16. If, in fact, point 27, which is the pivotal point about which beam 20 is deflected, does not fall precisely at the midpoint of 4the mechanical structure of coil 16, it does, for reasons readily understood, fall exactly midway, axially of the axis of the tube neck 11 of the magnetic field introduced by excitation of coil 16, and for this reason, the focal point of prior art tubes of this general type has been position Well within the neck portion 11 of the tube envelope 10.

As is readily apparent, beam 20 may be deflected as shown along path 24 only to the angular extent of contact with the inner wall of tube envelope at point 12, which represents the base of the flared section 13. It is equally obvious, as shown in Fig. 2, that substantial marginal portions of the end `vvall, as shown at 30, cannot be scanned by the beam, and therefore, serve no practical purpose. In other words, the flare angle of the envelope shown could be reduced without decrease of picture size. In view of this limiting feature, a flare angle as great as shown in Fig. 2 is not commonly employed.

With reference to Fig. l, a similar type of tube is illustrated and includes the tube envelope, generically designated 110, with the neck portion thereof designated 111 and the liared portion thereof, starting at 112, being designated 113. This portion of the tube may, for purposes of comparison with the structure of Fig. 2, but not by way of limitation considered to be identical in size and structure to the envelope of the Fig. 2 Structure.

As is evident from the figure, reference numeral 112 defines a throat intermediate portion 111 and flared portion 113 and it is the purpose of the invention to shift the position focal point 127 within at least the immediate vicinity of the throat as compared to the position of focal point 27, Fig. 2, which is positioned substantially aft of the throat designated 12. lt will be understood by persons skilled in the art that focal point 127 is located at what may be termed the magnetic center of an axially extending coil and while the magnetic center may not correspond in all instances to the physical center of the axial boundaries, the magnetic center which establishes the pivotal point, will in respect to the types of coils shown, closely approximate the physical center is measured from the axial extremities thereof.

The coils shown in Fig. l structure, generically designated 116, of which there are normally four in number positioned in quadrature. circumferential of the tube envelope to provide respectively the horizontal and vertical coil pairs, are of a configuration to complement the externa] configuration of the tube envelope 110 in a manner to effect the stated objective of positioning on magnetic focal point 127 within close to the throat 112. It will be noted that substantial portions of coil 116 lie along neck portion 111 while substantial portions thereof also lie along tnn dar-ed or frusto-conical portion 113. Coil '116 comprises a toroidal core 117 of suitable material, such for example as powdered. iron cr ferrite, and includes au aft portion 40, the inner surface of which is of concave configuration to complement the configuration of neck portion 111, shown as cylindrical, but not necessarily so. The forward end of core 117, as indicated at 41, is also provided with a concave inner surface which complements the configuration of ared portion 113, and since that portion is illustrated as of frusto-conical conguration, the inner surface of the forward core portion 41 is of a configuration to complement that configuration.

The invention is of course not limited to any particular configuration of the tubes envelope, so long as the envelope comprises an eiongate neck portion leading through a throat to an enlarged cud portion which serves to support, as above mentioned, a conventional photon emitting screen, not shown, but well understood in the art. Suitable windings 452, are externally applied over core 117 as shown in Figure l. Windings 42 may completely enclose core 117. lt is desirable that the windings extend substantially along core 117 to encompass not only a substantial axial portion of neck 11 but also a substantial portion of the flared envelope portion 113.

As is evident from the structure of Figure l, each coil 42 will normally be confined, as to circumferential dimension, to somewhat less than a quadrant of a circle, since it is common practice to allow spacing between each of the coils. While in most instances, four coils will normally be employed in certain types of cathode ray tube. such as those which currently find wide application in television receiving equipment, the inventive concept is not so limited, and for certain laboratory and other uses a single pair or even a single coil may be employed in the manner taught. Coil leads and the necessary winding exciting circuits have been omitted for purpose of simplification, such details and technique being too well known in the art to justify inclusion in the drawings.

An alternate embodiment of the invention is shown in Fig. 3, wherein a toroidal` core, generically designated 45, is of a configuration to conform to the external configuration of the tube envelope which includes a cylindrical neck portion 46 and a frusto-conical iiared end portionr 47. Core 45 includes a semi-cylindrical aft portion 48 and a dared forward portion 49 of semi-conical conliguration. Core 45 is positioned, by suitable supporting means, not shown, in spaced relation to the outer walls of the envelope at a distance to permit forward and aft disposition of yoke type deliecting coils, the sectional ends of one such coil being shown at Sil and 52 respectively, between core 45 and the envelope. Core 4S and coil 50 and 52 comprise each of, for example, four complete coil assemblies, normally limited in circumferential dimension to less than a quadrant of a circle, to function in the manner above described to position the magnetic focal point of an electron beam, shown unde liected at 54 and deflected at 55, to substantially the position shown at S6, which is adjacent, if not in registry, with the throat 57 of the envelope.

lt will be readily seen by persons skilled in the art that many other modifications and adaptations of the invention may be employed in conformance with known engineering expediency and manufacturing technique without departure from the spirit and scope of the invention, the concept of which is to position the focal point adjacent to the throat of an enlarged end envelope by application of the principles herein taught, and not necessarily by means of the structure which has been detailed for the purpose of illustrating those principles.

As is well known in the art, cathode ray tu-bes of the type herein illustrated `are conventionally 4employed at the aft end, not shown, with an electron emitting gun, the details of which are immaterial iin respect to the present inventiond Other details, such las the selection of core material, coil windings, and -tube envelope `configurati-on are also matters `of engineering expediency, hence an elaboration of such details would serve no useful purpose ri-n respect lto the -above disclosure.

What is claimed is z `1. In a cathode ray tube of the electromagnetic deflection type, thefcombination with an envelope including an elongate neck portion leading into an enlarged end .portion, Va toroidal core of magnetic material positioned circumferentially of said envelope with a substantial portion thereof `extending both along said neck portion `and along said enlarged end portion, and :a plural-ity of deliection coil windings operatively :associated with said core.

2. In a cathode ray tube of the electromagnetic deection type, the combination with an envelope including an elongate neck portion leading into an enlarged end portion, `of a toroidal magnetic core externally positioned circumferentially of `said envelope with a lsubstantial portion thereof extending both along said `neck portion and along said enlarged end portion, and deflecting coil wind-ings wound 4on said core.

3. 'In a devi-ce of the character described, an envelope includ-ing la cylindrical neck portion Ileading through la throat .to an enlarged f-rusto-conical end port-ion, and means establishing an elect-ron lbeam deliection focal point adjacent said throat, said means including a plurality of coils disposed in annular configuration about sai-d envelope, a lcommon core of a toroidal configuration to complement the envelope Iconfigura-tion for -a substantial distance on each side lof the throat, said coils comprising windings applied to said cores, and .means maintaining said coils externally of said envelope i-n a position to complement the conguration of said envelope.

4. In combination, a cathode ray tube including an envelope defining a general cylindrical neck portion and an integral lfrusto-conical end portion, a substantially toroid-al core of materi-al of high magnet-ic permeability including an aft port-ion provided with ia semi-cylindrical inner surface and a forward portion provided with a semi-conical inner surface, a plurality of magnetizing coils applied externally of said ycore to assume the con- 'figuration there-of rand to extend substantially over the entire surface thereof, whereby upon external applica- -tion of said coil to said envelope the `aft portion of said core complements the configuration of said neck portion Iand the forward portion of said `coil complements the configuration of said enlarged envelope portion in la manner to position .an electron ystream focal point adj-a.- lcent to the iuncture between said -above mentioned envelope portions.

l5. A cathode ray tube structure including an envelope having van elongate neck port-ion leading through a throat rand into la-n enlarged end portion of generally .frusto-conical contiguration, means disposed `within -s-aid elongate neck portion for the initiation and axial projec- Ition of lan electron beam along said `throat portion and into said frusto-conical end portion, and means Ifor the pivotal deflection of an initiated electron beam at a point substantially in registry with said throat, said means comprising `a ring :shaped core adapted to extend partially along said neck portion and partially along said frustoconical portion and to complement `the configuration of each said portion, means maintaining said core in spaced relation to `said envelope, vand plu-ral coils disposed intermediate said core and -said yenvelop-e, each of said coils being positioned Vto partially encircle said neck portion and to partially encircle said vrusto-conical portion.

References Cited n the tile of this patent UNITED STATES PATENTS Gunther Jan. 7, .4941 Bocciarelli Oct. 9, 1951 

